The international research team analyzed sediments from East Antarctica's Sor Rondane Mountains. They found that rocks newly exposed above the ice surface contain up to ten times more iron than previously reported elsewhere on the continent. This iron, carried to the ocean by glaciers and icebergs, serves as an essential nutrient for phytoplankton - microscopic marine organisms that absorb CO2 via photosynthesis.
The study determined that sediment from nunataks - mountain tops protruding through the ice - holds over three times more extractable iron compared to material already transported by glaciers. Iron concentrations were especially high in visibly rust-stained rock samples, pointing to weathering as a key process creating nutrient-rich sediment.
"Our results show that exposed bedrock in Antarctica acts like an iron factory," explained Dr Kate Winter, Associate Professor at Northumbria University and lead author. "Even though air temperatures rarely rise above freezing, sunlight can heat dark rock surfaces above 20 C in summer, creating the conditions needed for weathering and the formation of bioavailable iron compounds."
Fieldwork by Dr Winter was supported through a Baillet Latour Antarctica Fellowship. The research also highlighted the importance of this process through satellite observations, which revealed recurring phytoplankton blooms in coastal waters near glacier outlets, underlining the biological impact of this iron delivery mechanism.
Dr Winter added: "The exciting thing is that we can take some hope from these findings because we know that carbon dioxide is a really important factor in climate change. From our research we now know that sediments from the Antarctic continent could help to draw down atmospheric carbon dioxide into the ocean. Whilst our study area is limited to one glacier system, what we need to understand is the potential impact of these many small amounts being drawn down together across the whole of Antarctica. Piecing together information to gather an accurate picture of how much these natural systems are working to reduce the amount of carbon in the atmosphere is crucial."
However, the team, including scientists from Newcastle, Swansea, Plymouth, Edinburgh, and Leeds, cautioned that there is a substantial time lag. Modeling showed it could take between 10,000 and 100,000 years for the iron-rich sediments to travel from mountains to the sea via glaciers.
Dr Sian Henley from the University of Edinburgh noted: "While the sediments we examine in the mountains today will take a long time to reach the ocean, we know from seafloor surveys that iron-rich sediments have been delivered to the coast for millennia, so the processes we record today give us a glimpse into changes we might expect to see in the future, as glaciers thin and more mountain surfaces are exposed in Antarctica."
Their findings suggest that, with rising temperatures, the following factors will further boost iron delivery to the Southern Ocean: additional mountain peaks emerging as ice sheets shrink, increased rock slope failures supplying more sediment to glaciers, greater weathering producing more bioavailable iron, and icebergs dispersing these nutrients widely. This research expands understanding of the links between Antarctica's harsh physical environment and ocean ecosystems, as well as its role in the global carbon cycle.
Research Report: Thinning Antarctic glaciers expose high-altitude nunataks delivering more bioavailable iron to the Southern Ocean
Related Links
Northumbria University
Beyond the Ice Age
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